As a respiratory specialist, I can provide insight into the changes in oxygen levels during the night. Oxygen levels in the blood do tend to decrease slightly during sleep, which is a normal physiological response. This is partly due to a mild reduction in the level of breathing, known as hypopnea, that can occur during sleep. Additionally, some of the air sacs in the lungs, called alveoli, may not be fully engaged during sleep, leading to a slight decrease in the efficiency of oxygen exchange. However, for most healthy individuals, this is not a cause for concern. If a person's waking oxygen saturation is above approximately 94 percent, it is generally considered safe to assume that their saturation will not drop below the critical threshold of 88 percent during sleep. This is based on the assumption that there are no underlying health issues that could exacerbate oxygen desaturation. It's important to note that for individuals with certain medical conditions, such as sleep apnea or chronic lung diseases, the drop in oxygen levels during sleep can be more significant and may require medical attention. read more >>

Everyone's oxygen levels in the blood are lower during sleep, due to a mildly reduced level of breathing. Also, some alveoli drop out of use during sleep. If your waking oxygen saturation is greater than about 94 percent on room air, it is unlikely that your saturation during sleep will fall below 88 percent.read more >>